<!DOCTYPE html>
<html>

	<head>
		<meta charset="UTF-8">
		<title></title>
		<style>
			/*包含选择符所有a下的为红色*/
			.seon1 a {
				color: red; 
			}
			/*seon2变为黄色，相邻的同级元素*/
			.seon1+div {
				background: yellow;
			}
			/*第一个a显示绿色，子代选择符*/
			.seon1 > a {
				color: green;
			}
			/*兄弟选择符，Seon的同级兄弟显示绿色*/
			.seon1 ~ div {
				background: green;
			}
		</style>
	</head>

	<body>
		<div class="fader">
			<div class="seon1">
				<a href="">html</a>
				<div class="garndson">
					<a href="">css</a>
				</div>
			</div>
			<div class="son2">son2</div>
			<div class="son3">son3</div>
		</div>
	</body>

</html>